to Java 8 interface default methods • Elegant way to compose behavior • multiple inheritance without the « diamond » problem • Traits can also be stateful • traits can have properties like normal classes • Compatible with static typing and static compilation • class methods from traits also visible from Java classes • Also possible to implement traits at runtime 8
String fly() { "I'm flying!" } } ! class Bird implements FlyingAbility {} def b = new Bird() ! assert b.fly() == "I'm flying!" « trait », a new keyword for a new concept
String fly() { "I'm flying!" } } ! class Bird implements FlyingAbility {} def b = new Bird() ! assert b.fly() == "I'm flying!" the fly() method from the trait is available
{ 'kite' } } ! trait WebSurfer { String surf() { 'web' } } ! class Person { String name } ! class Hipster extends Person implements KiteSurfer, WebSurfer {} ! def h = new Hipster() assert h.surf() == 'web' extending a class and implementing the two traits
{ 'kite' } } ! trait WebSurfer { String surf() { 'web' } } ! class Person { String name } ! class Hipster extends Person implements WebSurfer, KiteSurfer { String surf() { KiteSurfer.super.surf() } } ! def h = new Hipster() assert h.surf() == 'kite' Your class method takes precedence over the traits
} ! class Animal {} class NamedAnimal implements Named {} ! def na = new NamedAnimal(name: 'Felix') ! assert na.name == 'Felix' Traits: runtime implementation 15 Somewhat artificial to have to create an intermediary class to get named animals
fact(BigInteger n, accu = 1G) { if (n < 2) accu else fact(n -‐ 1, n * accu) } ! assert fact(1000) > 10e2566 Downside of tail recursion is you might have to rewrite your algo to be tailrec friendly
int meaningOfLife = 42 } @BaseScript(CustomBase) import groovy.transform.BaseScript ! assert meaningOfLife == 42 You can add your own base methods and properties to all compiled scripts
int meaningOfLife = 42 } @BaseScript(CustomBase) import groovy.transform.BaseScript ! assert meaningOfLife == 42 Define the base script class for this script
int meaningOfLife = 42 } @BaseScript(CustomBase) import groovy.transform.BaseScript ! assert meaningOfLife == 42 Ability to put the annotation on imports & package
File retrofitted on Path as well 24 path.withReader { Reader r -‐> ... } path.eachLine { String line -‐> ... } path.eachFileRecurse { Path p -‐> ... } path << 'some content' path << bytes path.readLines() … Feature request to add all the java.nio.file.Files static utility methods as GDK
support for speed & efficiency • parser forked off the Boon JSON project • serializer carefully fine-tuned ! • Article on the parsing speed improvements • http://rick-hightower.blogspot.fr/2014/04/groovy-and-boon-provide-fastest-json.html 26
support for speed & efficiency • parser forked off the Boon JSON project • serializer carefully fine-tuned ! • Article on the parsing speed improvements • http://rick-hightower.blogspot.fr/2014/04/groovy-and-boon-provide-fastest-json.html 26
support for speed & efficiency • parser forked off the Boon JSON project • serializer carefully fine-tuned ! • Article on the parsing speed improvements • http://rick-hightower.blogspot.fr/2014/04/groovy-and-boon-provide-fastest-json.html 26 Benchmark gives 3x to 4x performance factor over Jackson and GSON
support for speed & efficiency • parser forked off the Boon JSON project • serializer carefully fine-tuned ! • Article on the parsing speed improvements • http://rick-hightower.blogspot.fr/2014/04/groovy-and-boon-provide-fastest-json.html 26
! • Additional parsing modes: • INDEX_OVERLAY: super fast for <2MB payloads o using a « parsing overlay » technique • CHARACTER_SOURCE: for >2MB payloads o implemented with sliding windows over readers • LAX: beyond the JSON spec, nice for configuration files o support single quotes, / and # comments • CHAR_BUFFER: general purpose 27
« builders » • and particularly the MarkupBuilder class for generating arbitrary XML / HTML payloads ! • Compiled statically for fast template rendering ! • Internationalization aware • provide the desired Locale in the configuration object • usual suffix notation template_fr_FR.tpl ! • Custom base template class • ability to provide reusable methods across your templates 30
« builders » • and particularly the MarkupBuilder class for generating arbitrary XML / HTML payloads ! • Compiled statically for fast template rendering ! • Internationalization aware • provide the desired Locale in the configuration object • usual suffix notation template_fr_FR.tpl ! • Custom base template class • ability to provide reusable methods across your templates 30 Spring Boot approved
cars.each { car(make: it.make, name: it.name) } } model = [cars: [! new Car(make: 'Peugeot', name: '508'), ! new Car(make: 'Toyota', name: 'Prius’)! ]] Feed a model into your template
use createTypeCheckedModelTemplate() instead of createTemplate() ! • Advantages • get compilation errors o if a variable is not available o if you make mistakes in the code snippets • even faster templates 34
apps! • use Groovy 2.4.0-beta-1+ • prefer @CompileStatic ! • Two great posts to get started: • http://melix.github.io/blog/2014/06/grooid.html • http://melix.github.io/blog/2014/06/grooid2.html 42
macro module • https://github.com/groovy/groovy-core/pull/470 ! • Simplify creation of AST transformations • less boilerplate manipulating the Groovy AST API • more powerful and less limited than AstBuilder 45
46 def someVariable = new ConstantExpression("xyz") def returnStatement = new ReturnStatement( new ConstructorCallExpression( ClassHelper.make(SomeCoolClass), new ArgumentListExpression(someVariable) ) )
JDK 7+ invoke dynamic • get Java-like performance even for dynamic code • Rationalize the sedimentation of meta-programming • more coherence, less corner cases & inconsistencies • Provide a notion of « realm » • shield users of « monkey patching » • finer-grained control of meta-programming reach • Private visibility anyone? 51
v2! o but version 3 and 4 are out • Groovy’s grammar evolved from a Java grammar o harder to fix and evolve, especially with Antlr v2 • Advantages • Start from a clean slate • Antlr 4 more tolerant and powerful regarding ambiguities • Time to clean some grammar & syntax warts! • Need to implement the Java 8 constructs! 53
v2! o but version 3 and 4 are out • Groovy’s grammar evolved from a Java grammar o harder to fix and evolve, especially with Antlr v2 • Advantages • Start from a clean slate • Antlr 4 more tolerant and powerful regarding ambiguities • Time to clean some grammar & syntax warts! • Need to implement the Java 8 constructs! 53 A « Google Summer of Code » student helped kick start it
support • to keep saying Groovy / Java interoperability is awesome! • New in Java 8 • lambdas • method references • default methods in interfaces • stream API, date / time API • annotations on types & repeated annotations 55
support • to keep saying Groovy / Java interoperability is awesome! • New in Java 8 • lambdas • method references • default methods in interfaces • stream API, date / time API • annotations on types & repeated annotations 55 Groovy had already: closures, method pointers, mixins, enriched collection & time APIs